Draft control system



June 20, 1933. PEEBLES 1,915,101

DRAFT CONTROL SYSTEM Filed June 19, 1931 3 Sheets-Sheet l INVEN TOR.

we ATTORNEYS.

J1me 1933. 'r. A. PEEBLES JDRAFT CONTROL SYSTEM Filed June 19, 1931 3 sheets sheet 2 W M m M A TTORNEYS.

June 20, 1933. @EEBLES 1,915,101

DRAFT CONTROL SYSTEM Filed June 19. 1951 3 Sheets-Sheet 3 IgVlflTOR. y awwmm JLLW ATTORNEYS.

Elli

Patented June 20, 1933 UNITED STATES PATENT orrica THOMAS A. PEEBLES, OF MOUNT LEBANON, PENNSYLVANIA, ASSIGNOB TO JOHN HOPWOOD, 0F DORMONT, PENNSYLVANIA DRAFT CONTROL SYSTEM Application med nine 19, 1931. Serial No. 545,425.

This invention relates, in general, to boiler furnaces and more particularly to the control of dampers and blowers therefor.

In the operation of boiler furnaces air for combustion is supplied either by' forced or induced draft mechanisms, or by both forced and induced draft. In either case, motor driven fans are employed.

Practical experience has demonstrated that satisfactory control of the draft cannot be obtained by adjustments of fan or blower speeds only. The ordinary type of motor employed for such service is adapted to operate at only a few speeds between maximum and minimum, whereas the load carried by a boiler furnace at any instance may require a fan speed that lies between the s eeds at which the motor will operate. If am er control is not used,.it would only be possi le to 0 erate the boilers eificiently at a series of etinite ratings depending upon the air or as handling capacit of the fan when running at the speed available by the type of motor employed. This is an unsatisfactory condition.

There is a certain interval between the time a change in motor speed is initiated and the time the motor actually comes to the new speed, giving the fan or blower a new air or gas handling capacity. This interval should be reduced to the shortest possible time to prevent hunting of the motor relating equipment, and this is best employs by employlng damper control.

it is customary therefore to sheet draft control by a combination of fan speed and damp er regulation. An arrangement commonly employed includes an electric controller so arranged that when the damper or the reg-- ulator handling the damper reaches a predetermined open position, the speed of the fan motor will be increased. The increased speed of the fan increases the amount of air or gas handled and this amount exceeds the amount actually required, causing the regulator to reverse its direction of travel and to open again finally reachinglthe point where position as outlined above and may be pointed out as follows:

Assume that the boiler is operating at minimum load with the fan operating at minimum speed and the damper near its closed position. As the load on the boiler increases, the damper is gradually opened but a point is soon reached where further movement of the damper not effective to increase the furnace draft. When the fan is running at a low speed, this position may be only 15 or 20 degrees of damper opening. it will be apparent that if the duct in which the damper is placed is large enough to handle allthe air or gas the fan can deliver when running at full speed, this duct will be very much larger than is required to handle the air delivered by the fan when run "ning at minimum speed. The result is that a small movement-of the damper gives all the regulation that can besecured while the tan is operating at low speed. It will be apparent that with the arrangement commonly used for this purpose it is necessary for the regulator to continue opening the damper until it approaches its wide open position before the speed of the fan will be increased. The result is that throughout a large portion of the strokeof the regulatorno efi'ective control of the damper will be obtained. a

On the other hand, if the furnace is operating at its maximum load with the fan at full speed and the damper wide open and the boiler load drops oil, the damper is gradually closed but no reduction in fan speed will take efiect until the damper approaches its closed position. The result is that a comigher predeter- Y paratively low load might be carried by the boiler, but the fan will be operating at full speed. In this case a large amount of throttling takes place at the damper. The motor driving the fan is therefore operating at an excessive speed and load resulting of course in a loss of power which it is desirable to avoid.

An object of this invention, generally stated, is to provide for maintaining the proper relation between the speed of a fan or blower and the position of the damper at which blower or fan speed changes will occur.

Another object of the invention is the provision of a damper and fan speed control so arranged that for each position of the damper the blower or fan will be operated at such a speed that the volume of air or gas handledthereby may be effectively regulated by small adjustments in the damper position.

Other objects of the invention will, in part, be apparent and will, in part, be obvious from the following specification and the. drawings forming part hereof.

The invention comprises the details'of construction and the novel arrangement of circuits and apparatus as illustrated in the accompanying drawings in which:

Figure 1 is a schematic illustration of a boiler furnace and apparatus for controlling or regulating the position of dampers and the speed of fan blowers utilized to supply and control the amount of air and gas supplied to and taken from the furnace;

Fig. 2 is an assembled View, partly in section, of a regulator embodied in the system shown in Fig. 1; and

Fig. 3 is a diagrammatic illustration of circuits and apparatus employed for controlling the speed of the blower or fan motors shown in Fig.1.

Throughout the drawings and specification like reference characters indicate like parts.

In Fig. 1 of the drawings a. boiler furnace 1 is shown having forced and induced draft mechanisms 2 and 3, respectively. The steam generated by the boiler is delivered to the usual header H.

The forced draft mechanism comprises a blower or fan 4 driven by a variable speed motor 5, preferably an electric motor. The

speed of motor 5 may be adjusted or varied by means of a controller 6 which is schematical- 1y illustrated in Fig. 3 of the drawings.

Blower or fan 4 blows or forces air into the furnace through a conduit 7 having a damper 8 therein. Damper 8 may be operated or ad,-

' justed from open to. closed positions, or vice versa by an actuating means 9. The type of actpating means illustrated may be a pressure responsive regulator arranged to res nd to the pressure within the furnace com ustion chamber. The furnace chamber pressure may be transmitted to the pressure responsive elethereof is either decreased or increased unt'l the pressure within the chamber is restored to a predetermined value. For operating reasons it is desirable to maintain the aforesaid furnace pressure substantially c instant.

In order that damper 8 may be effective, when adjusted to. any position, to control the flow of fluid or air through conduit 7, the quantity flow of such air or fluid must be adjusted in proportion to the degree of damper opening, or in other words, in proportion to the position of the damper.

For example, if a large quantity or volume of air or fluid is flowing through conduit 7 and the damper is in its full open position, a

. small movement of the damper will materially decrease the flow of air through the conwide open, small movements of the damper towards closed position will have practically no effect upon the quantity of air flowing. In the latter case, the damper is ineffective to change the quantity of air flowing until it is practically in its closed position.

In order that damper 8 may be effective to change or regulate the quantity'of air or fluid flowing when adjusted to any position whether such )osition be substantially the closed, the wi e oicn, or any intermediate position, the quantity or volume of air flowing should be apportioned in accordance with the position of the damper.

In the present case, since blower 4 is a source of forced draft, the speed of the blower should be adjusted to deliver a large volume of air to the furnace when the dam )er is in or near its wide open position; a relatlvely small volume of air, when the damper is in or near its closed posltion; and intermediate volumes when the position of the damper is between the wide open and the closed positions. In

other words, it is proposed to adjust the speed iver different quantities or volumes of air or fluid for different positions of the dam r. In each case, the volume or quantity of uid or air delivered will be so apportioned that small movements of or adjustments of thedamper will have an appreciable regulating effect upon the volume flow of the air or Y fluid.

If the speed of the blower is varied or adjusted as indicated above, the quantity of air flowing for an given blower speed may be varied b smal adjustments or changes in. the position of the damper.

trolling device 11 is so arranged that it may be moved bodily by the actuatin means, when it has moved a predetermined amount, in either direction. I

The circuit controlling device 11 governs the operation of motor controller 6 and is so arranged that, for any given position of the damper, the speed of motor 5 may be inreased or decreased in response to small deviations in furnace pressure that may take place while the damper is in any articular position. For each positionof tlle circuit controlling device 11, theblower motor is caused, by its controller 6, to operate at adifi'erent predetermined speed.

Since the pressure responsive actuating means 9 operates directly u on the damper, it will be apparent that tie speed of the blower 4 will/be adjusted to a value corresponding to the position, degree or amount of damper opening.

The induced draft mechanism 3 comprises a blower or fan 12 that is driven by a variable speed electric motor 13. Blower or fan 12- draws air and products of combustion from the iurnace'chamber through a conduit is having; a damper 15 therein and discharges such air and products of combustion into a conduit 16 that is connected to the usual stack (not shown).

Damper 15 may be operated or adjusted by an actuating means 17 similar to the actuating means, 2. Actuating means 17 may be arranged to respond to the demand forsteam' upon the boiler and to the pressure obtaining in the furnace chamber at the oint wherecon duit 14 hasicommunicationt erewith. Pres sure from the furnace chamber in the region of conduit is may be communicated to a pressure responsive element of actuating means 1'? through a conduit or pipe 18.

In order that the actuating means 17 may be so modified that it will adjust damper 15 by and in accordance with the demand for steam as well as in accordance with variations in pressure in the furnace uptake, a master regulator 21 is provided. Master regulater 21 is so arranged that it eii'ects a reduction in pressure withinbellows 19 when the steam pressure falls and the demand. for steam increases and an increase in pressure within the bellows when the steam pressure rises and the demand for steam decreases. Master regulator 21 comprises a pressure responsive or metering device 22 such as illustrated United States Patent No. 1,3? 1,243 granted March 15, 1921, "to John M.

area thereof bearing on and under pressure.

Fopgwood and a master pressure sending reevice 22 includes a weight arm 24 that is acted upon by a pressure diaphragm 25 in one direction and in the opposite direction by an opposing pressure diaphragm 26. Pres sure diaphragm 25-is subjected to the steam pressure in header H of the boiler, whereas iaphragm 26 is acted upon by'a constant pressure confined within a bellows or drum 26 Diaphragm 26 is of such shape, as described in said Patent No. 1 371,243, that the in contact with a plate 27, 'inte osed between said diaphragm and weig t arm 24, varies as the pressure on diaphra m 25 varies. Thus, any movement of wei h? arm 24; will be directly proportional to t e pressure acting on diaphragm 25, hence, directly proportional to the steam pressure in header H.

Master pressure sending relay 23 comprises a pressure responsive bellows 28 and a valve 29 having a valve plug 30 thcreinjointly controlled by the bellows and the weight arm 24.

Valve plug 30 has a valve stem 31 connected to one end of a floating lever 32, the other end of said lever being connected by a link 33 to weight arm 24.

Bellows 28 1s rovided with a push rod 34' the upper end of which is connected to floating lever 32 between the ends thereof, thus lever 32 may pivot about its connection 33 or about its connection with push rod 34.

Bellows 28 operates against a spring'35' so that the amountit expands or contracts will be substantially directly in proportion to the pressure applied to the interior thereof.

alve 29 has a port which is connected to a pipe line 36' having therein a supply of fluid Valve 29 also has an outlet port connected by a pipe 37 to a pipe line 38 whereby pressure variations may be communicated to bellows 19. Pipe line 38' is in communication with the interior of bellows 28 and the interior of bellows 19.

When the pressure in steam header H rises lever 24 moves clockwise, thereby turning fioatin lever 32 counterclockwise about its pivotafconnection with push rod 34' thereby Elli lid moving valve plug 30 downwardly until pressure flows from supply line '36 through pipe 3? to the interior of bellows 28 and ug 30 will rise causing pressure in pipe line.

38 and bellows 28 to exhaust through pipe 37 and exhaust port 39' in valve 29 to the atmosphere, thereby reducing the pressure in bellows 28 and pipe line 38'.

As the pressure is reduced, spring 35 will cause the bellows 28 to collapse, thereby turning valve lug 30 to its neutral position in which position further exhausting of pressure from bellows 28 and pipe line 38 to the atmosphere is prevented until the pressure in the steam header falls again to a lower value.

In the resent case, it is proposed to maintain the ibrce acting on actuating means 17, as affected by the pressure in conduit 14, in equilibriuin'with the force acting thereon by bellows 19. If for any cause, this equilibrium is disturbed, means .17 will operate to adjust damper 15 until equilibrium is again restored. i

In order that movements of the actuating means 17 caused either by the presure act ing through bellows 19 or the pressure acting through pipe line 18, or both, may be utilized to control the operation of motor 13 in accordance with the position of damper 15, a circuit controlling device 11 is provided. Circuit controlling device 11' operates in the same manner as circuit controlling device 11 and is arranged to be moved bodily by the actuating means 17 when it has moved a predetermined amount in either direction. Circuit controlling device 11 controls the operation of a motor controller 6' that is similar to controller 6. Controller 6 is illustrated schematically in Fig. 3 of the drawings and operates to adjust the speed of motor 13.

In Fig. 20f the drawings, regulating device or actuating means 17 is illustrated in detail.

Devices 17 and 9 are, in the present case, identical except for the bellows 19, the bellows. being omitted in device 9. Since these devices are otherwise identical, the description of device 17 will be suflicient for both.

Device 17 comprises a pressure responsive element 34 and a fluid-pressure motor or re 'ulator 35. Y 5

lhe pressure responsive element comprises a lever or beam 36 mounted on a. fulcrum 37, and inverted bells 38 and 39 mounted at opposite ends o the beam. Bells 38 and 39 are partially immersed in liquid 40 containedin a tank 41 having a suitable cover 42. Bell 38 has an interior chamber 43 that is'open at the top and closed at its bottom. An orifice 44 is provided in the bottom of chamber 43 in which a needle valve 45 is adjustably disposed.

Bell 39 likewise is provided with an in terior chamber 47 having a needle valve orifice48 and needle valve 49 in its bottom.

WVhenbells 38 and 39 areat rest, fluid in ,the tank 41 will flow through the needle valves into chambers 43 and 47 until the level of the fluid therein is equal to the level of the fluid in the tank. If lever or beam 36 is caused to turn on its fulcrum, thereby raising one of the bells and lowering the other, the fluid in the bellwhich is being raised will gradually flow out through its needle valve, gradually decreasing the retarding effect of such fluid to upward movement of the bell. The hell on the opposite end of the lever which is being lowered and submerged, offers resistance to 7 of bells 38 and 39 is clearly disclosed in my U. S. Letters Patent No. 1,800,400 granted April 14, 1931.

The retarding effect of the interior chambers on the movement of bells 38 and 39 may be adjusted by means of the needle valves 45 and 49, respectivel The interior of hell 39 has communication with pipe 18 and is therefore subjected to the pressure in ionduit 14, whereas, the interior ell 38 has communication with the atmosphere through a pipe 50. The interior of hell 38 is therefore subjected to a constant pressure while the interior of bell 39 is under a pressure which may yary from time to time as the pressure in conduit 14 changes. In response to changes pressure within bell 39, lever or beam 36 will turn in one direction or the other dependingiupon the direction of change in pressure. ovements of beam 36 are utilized to control the operation of fluid pressure motor or regulator 35.

Fluid motor or regulator 35' comprises a cylinder 52 having a piston therein (not shown) and a frame 53 carried by a piston rod 54 attarhed to the top face of the piston.

Motive fluid, such as compressed air, may be, admitted to either side of the piston by means of a valve 56, the motive fluid entering the valve through an inlet port 57. Valve 56 has a valve stem 58 which, when moved downwardly and below the closed position of the valve, opens the valve to admit air or fluid under pressure to the cylinder at the bottom face ofthe piston; and when moved upwardly above the closed position, fluid under pressure is admit-ted to the cylinder at the top side of the piston.

When fluid is'admitted to the cylinder at the underside of the piston, piston rod 54 moves upwardly carrying with it frame 53;

and if the fluid is admitted to the cylinder at the top side of the piston the piston rod moves downwardly carrying the it. As will be apparent from Fig. 1, upward and downwardmovements of frame 53 are rame with.

I utilized to. shift the position of the damper connected thereto.

In order that movements of beam 36 may be utilized to operate valve 56, a connectin rod 59 is provided, which, operating throug lever 60, bell crank 61, connectin link 62 and stem 58, actuates the valve. 1 connecting rod 59 moves upwardly, lever 60 is turned in a counter-clockwise direction whereby valve stem 58 is moved downwardly. Downward movement of connecting rod 59 results in upward movement of the valve stem.

If valve stem-58 has been moved downwardly so as to .admit fluid to the cylinder at the underside of the piston, frame 53 will move upwardly. In order that the valve may be returned toits closed position when the frame 53 has moved a predetermined distance, an angling bar 64, carried by frame 53,-

and a lever 65 are provided. Angling-bar 64 is ivotally mounted medially of its ends on a racket 66 carried by frame 53. The

upper end of bar 64: may be secured in a yoke 67 bymeans of a wing nut 68. In order that the angle to which bar 64 is inclined may be adjusted, an adjustment screw 69 is provided. By loosening wing nut 68 and turning screw 69 into or out of the yoke, bar 64 may be turned about its pivotal support in bracket 66 to the proper angle. When adjusted to the proper angle, the wing nut is tightened to securely hold the bar in its adjusted position.

Bar 65 is pivotally mounted at its lower end in a bracket 71 carried at the lower end of cylinder 52. The upper end of bar 65 carries rollers 72 disposed on opposite sides of the angling bar 64. Therefore, as frame 53 moves up or down, carrying with it angling bar 64, lever 65will turn about its pivotal support. If the frame 53 moves upwardly, bar 65 will be turned in a clockwise direction; and in a counter-clockwise direction if the frame moves downwardl Bar 65'is connected to bell cranZ 61 by a link 73 which is moved to the right when bar 65 turns in, a clockwise direction and to the left if the'bar isturned in a counterclockwise direction.

I f valve 56 has been opened to admit fluid pressure to the underside of the piston in cylinder 52, frame 53 will move upwardly causing angling bar 65to turn in a clockwise direction as aforesaid, carrying with it link 73. Movement of the link 73 to the right rauses bcll' crank 61 to turn in a counter.

clockwise direction moving valve stem 58 upwardly and closing the valve, whereby the pressure to the cylinder is shut 01f. If the valve is again opened to admit pressure to to the underside of the piston, frame 53 will move upwardly a predetermined distance be f ore the valve closed again. The length of travel of frame 53 is determined by the rate of closing of the valve when the frame is moving inone direction or the other; and the If frame 53 is moving in a downward direction in response to successive openings of.

valve 56, ang ing bar 64 acting through bar 65 and link 73 will cause the valve to close when the frame has traveled a predetermined distance after each opening of the valve.

From the above, it will be apparent that frame 53 may be caused to move in incremental steps in either direction throughout the full stroke of the piston rod 54.

As shown in Fig. 2 of the drawings, the bellows 19 is mounted on the framework of regulator 17. The lower end of the bellows is connected by a link 76 tobeam 36. Therefore, as the pressure admitted to the bellows through pipe line 38 increases or decreases, the bellows will expand or contract, as the case may be, and impose a turning force upon the beam. By properly adjusting the mechanism-which operates valve 29, bellows 19 may be caused to act on beam 36 in the same direction as the force of the suction pressure in float or inverted bell 39 acts on the beam. In. other words, beam 36 may be caused to move in. response to the difference of the forces imposed thereon by the bellows 19 and the pressure acting on float 39.

In practice, it may be desirable to have beam 36 in a condition of stable equilibrium when certain conditions exist in the steam header H and induced draft conduit 14. To place beam 36 in equilibrium, when such conditions exist. a counterweight 77 may be mounted on beam 36 at the opposite side of fulcrum 37 from which float 39 and bellows 19 act on the beam.

Since circuit controlling devices 11 and 11 are similar in construction, the same referencecharacters will serve to identify like or similar parts.

Circuit controlling device 11' comprises stationary contact members 78, 79 and a yieldably movable contact member 80, that a bracket 85 having an adjustable stop 86 is provided and secured to frame 53. When frame 53 has moved upwardly a predetermined distance,the adjustable stop 86 engages the upper L-shaped end of bar 82 and moves it bodily upwards whereby circuit controlling devicell' is bodily moved upwards. The length of travel required of frame 53 before bar 82 is moved upwardlymay be adjusted by shifting the adjustable stop 86 up or down in the bracket 85.

In order that bar 82 maybe moved downwardly when regulator 53 has moved a predetermined distance, a bracket 87 is secured to regulator frame 53 and carries an adjust able stop 88 which is disposed to cooperate with the lower L-shaped end of the bar. Therefore, when regulator frame 53 has moved downwardly a predetermined distance bar 82 will be moved downwardly carrying with it circuit controllin device 11'-. I

As will be observed rom Fig. 2 of the drawings, one end of yieldable contact member 80 is rigidly secured to block 81 and carries a roller 89 at its free end. Roller 89 is disposed in the ath of movement of cam blocks 90 carrie by regulator frame 53. Blocks 90 are so arranged that when frame 53 has moved a predetermined distance in the upward direction, the lower block will engage roller 89 and cause contact member 80 to contact with contact member 78. Likewise, if frame 53 is moved downwardly a predetermined distance, upper block 90 will engage roller 89 and cause contact member 80 to engage contact member 79.

If the furnace suction, as measured in'the furnace uptake 14 decreases, float 39 will rise thereby moving valve operating rod 59 downincreased opening of damper 15, the regulator frame 53 will move downwardly until lower stop 86 engages the lower L-sha ed end of bar 80 and move circuit control ing device 11 downwardly to a lower position. During such downward movement, contact members 79 and 80 are held closed, thereby causing the induced draft fan motor 13 to increase its speed as damper is being opened.

If uch increased fan speed and increased dam er opening has increased the suction in upta e14 to a value slightly above that requircd, float 39 will move downwardly whereby valve 56 will be shifted to that position in which framc 53 will be moved upwardly to close damper 15. p

The moment regulator frame 53 moves upwardly, contact is broken between contact members 79 and 80, but contact therebetween is broken at a'lower point in the travel of the regulator than that at which contact was originally made. The electric control circuit being broken between contact members 79 and 80, the speed of motor 13 driving fan 12 will not be further increased, although the motor I tinues to increase above that required, regulator frame 53 will continue to move upwardly and gradually close damper 15. When, in t 1e upward travel of frame 53, lower block 90 engages roller 89 and closes contact members 78 and 80, a control circuit is established that operates to decrease the speed of motor 13 and fan 12. If the suction is still too'high, frame 53 will continue to move upwardly to close damper 15 and when ithas moved a predetermined distance, upper'stop 86 engages the upper L-shaped end of bar and carries device 11 bodily upwards to a higher position.

Thus, the moment the frame starts downwardly, contact members 79 and 80 will be disengaged, but the fan motor will continue to operate at the speed it had attained before these contact members were separated. It is to be noted, that when contact members 7 9 and 80 are disengaged, the circuit controlling device 11 occupies a higher position than that at which contact was made thercbetween at the beginning of the upward stroke of regulator frame 53. 4

Thus, it will be apparent that when frame 53 is moving in one direction and contact is made either between contact members 79-80 or 78-80, and the frame continues to move in that direction, the circuit controlling device will be shifted bodily in the same direction. Therefore, when the motion of the regulator frame is reversed, the contact members which were closed will be opened when the regulator frame has moved only a relatively short distance in the reverse direction. T hereforc, it will be apparent that the circuit control device 11 is always shifted to such a position that contact between either cont-actmember 79-80 or 78-80 is always broken at a point in the stroke of the regulator which is removed from the point in the regulator stroke at which contact was'originally made.

It will be understood that each time valve 56 is opened either to cause the regulator frame to move upwardly or downwardly, angling bar 64 and link 73 operate on bell crank 61 in such a manner as to close the valve when the regulator frame has moved a predetermined distance. By so controlling valve 56, regulator frame 53 will move stepby-step in one direction or the other depending upon the position to which the valve is actuated.

If the general movement of frame 53 is upward, contact will be made and broken ingtarmittently between contact members 78 and Likewise, if the general movement of frame 53 is downward in response to lowering movements of bell 38, either because of a reduction in pressure within the bell or because of increased pressure in bellows 19, the circuit through contact members 79 and will be made and broken intermittently.

7 shown in Fig. 1, regulating devices 9 and 17 are so adjusted thatthe proper amount of air is supplied to the furnace to satisfy come bustion requirements. Also regulators 9 and 17 are so arranged that a substantially constant pressure may be ma ntained in the furnacev combustion chamber. When the ressure in the combustion chamber varies rom this constant value, device 9 responds and operates damper 8 to a predetermined position to permit the proper amount of air to pass into the furnace. Device9 also operates to adjust the speed of the blower motor 5 to such a value that blower 4 will deliver that amount of air which can be effectively changed or regulated by a small change or adjustment in position of the damper.

If, for example, the load demand on the furnace is such that a reduction in pressure within the furnace takes place, bell 38 of regulator 9 will lower, causing frame 53 to lower in the manner aforesaid. As frame 53 moves downwardly, damper 8 is shifted towards the open position. When the frame. lowers, upper block will close contact members 7 9 and '80 causing motor re ulator 6'to operate and increase the speed 0 motor 5 and the fan or blower 4. The increased speed of the blower is such that the amount of air passing damper 8 may be regulated effectively in response to small changes in position of the damper. 7

7 If the position to which damper'8 has been moved is such'that the pressure in the furnace is increased. float 38 will rise. Regulator frame 53 will, therefore, move upwardly opening contact members 79 and 80. Motor 5, however, will continue to operate at the aforesaid increased speed.

When the pressure in the furnace rises above the value to be maintained therein, float 38 will rise to a higher position and regulator frame 53fwill move upwardly in the i manner aforesaid thereby closing damper 8 in proportion to the amount that the frame 53 is moved. If'the frame moves upwardly a predetermined distance, contact will be made between contact members 78 and 80 whereby motor regulator 6 will operate to.

reduce the speed of motor 5. At this redueed speed blower 4 will deliver that amount of air which can be effectively regulated by small changes in position of the damper 8. J 1

Fromthe above description, it willbeapparent that for each change in position of damper 8, the speed of blower 4 will be changed in the same direction as the direction of movement of the damper. It will be apparent also from the description of Fig. 2, that regulator frame 53, when moving a predetermined amount in either direction, will move the circuit controlling device 11 to a certain position. Therefore, for each position of frame 53, there will be a definite damper position and blower .speed.

By the particular construction of the regulater, it is possible for contact to be made intermittently. between contact members 78 and 80 and 79 and 80 without movingbar 82 which carries the circuit controlling device. Thus, for any given position towhich damper 8 may be moved, the speed of. the blower 4 may be increased or decrease by predetermined amounts without changing the position of the circuit controlling device.

If damper 8 is-moved to approximately its closed position, the speed .of blower 4 will be lowered to such a value that the quantity of air passing the damper may beregulated effectively even though the damper is shifted only a relatively small amount. Likewise, if the damper h'ps been actuated to approximately its wide open position, the speed of blower 4 will be increased to such an extent that the volume of air flowing past the damper may be effectively regulated even though the damper is moved only a relatively small amount. And for each intermediate damper position there will be an intermediate blower speed corresponding to the position of the damper.

In Fig. 3, the circuits and apparatus employed for controlling blower motor 5 are diagrammatically illustrated. As shown, field winding F of motor 5 is connected in series with a resistor 92 across supply conductors 93 and 94. The speed of motor 5 may be increased or decreased by bridging or shunting sections of the resistor. For the purpose of shunting the resistor, a drum 95 may be employed that is driven by a motor 96 through gearing 97.

Motor 96 may be of the simple split-fieldtype reversible motor. For purposes of illustration, motor 96 is provided with field windings 98 and 99.

When field winding 98 is energized and the armature of the motor is connected across the 1 decreasing the resistance series with field winding F and decreasing the speed ofmotor 5.

If field winding99 is energized motor 96 I will operate in the opposite or reverse direction, in which case drum 95 will be moved in direction of arrow 101. The drum, moving inthis direction, will insert a section or sections of the resistor in series with field winding F of motor 5 thereby weakening the magnetic field of the motor. The speed of the motor will, therefore, be increased.-

If regulator frame 53 is moving in the upward direction and contact is made be- "tween contact members 78 aud.80, a circuit is established whereby a solenoid 102 of a time delay relay 103 ,is energized. Upon the closure of this relay, solenoids 104 and 105, respectively, of contactors 106 and 107 are energized. Upon the energization of these solenoids, contactors 106 and 107 will close, connecting field winding 98 and the armature of motor 96 across supply conductors 93 and 94. Drum 95 will then be advanced in the direction of arrow 100 to decrease the ed dash pot 109.

Solenoid 102 of relay 103 is controlled by contact members 78 and 80; but when this relay is closed, a circuit is established shunting contact members 78 and 80 and connecting solenoids 104 and 105 across supply conductors 93 and 94. Therefore, if, after contact has been made between contact members 78 and 80, contact should be momentarily broken therebetween. solenoids 104 and 105 will remain energized for a predetermined length of time, the length of time being determined by the length of time required for the spring loaded dash pot 109 to open the contact members of time delay relay 103.

From the above, it will be observed that if the generalmovement of regulator frame 53 is upwards and momentary contact is made and broken intermittently between contact members 78-and 80. motor 96 will be energized intermittently. Each time the motor is en ergized, it will operate for such a length of time that at least one section of resistor 92 will be bridged or shunted out of the circuit of field winding F of motor 5. Therefore,

C3 the. speed of motor 5 will be decreased stepby-step as damper 8 is closed step-by-step by the regulator or device 9.

If the pressure in the furnace is decreasing below the value to be maintained therein,

C5 float 39 will lower and move connecting rod 59 downwardly. As stated previously herein, downward movement rod 59 causes valve stem 62 to move upwardly whereby fluid 7 under pressure is admitted to the cylinder 52 at the to side of the piston therein. Frame 53 will t en move downwardly a predetermined distance and will come to rest when the angling bar 64 has operated to close the valve.

If the distance which frame 53 has moved downwardly is not great enough to cause contact members 79 and 80 to close, motor will continue to operate at that speed at which it was operating before the regulator moved downwardly. However, dam er 8 will be opened to permit more air to ow to the furnace. If the downward movement of frame 53, however, is great enough to cause contact members 79 and 80 to close, a. circuit will be established for energizing a solenoid 110 of a time delay relay 111. Upon the closure of relay 111, solenoids 112 and 113 of contactors 114 and 107 are connected across supply conductors 93 and 94. Contactors 114 and 107 will, therefore, close to connect field winding 99 and the armature of motor 96 across the supply conductors 93 and 94. Motor 96 will then operate in such a direction as to move drum 95 in the direction of arrow 101, thereby to insert a section or sections of resistor 92 in series with field winding F of motor 5. The

current in field winding F will therefore be decreased and motor 5 will operate at increased speed. From the above it will be observed that damper 8 has been opened a.

predetermined amount. It will also be observed that the speed of motor 5 has been increased an amount depending upon the amount that damper 8 was opened.

In order to insure that contactors 114 and 107 will remain closed for such a length of time that at least one section of resistor 92 will be inserted in series with the field winding F of motor 5, time delay relay 111 is provided with a spring loaded dash pot 115.

The energization of solenoid 110 of relay 11 is controlled by contact members 79 and 80, but the energization of solenoids 112 and 1 to open the contact members of time delay relay 113 when the time period has elapsed and this period should be sufiicient to permit motor 96 to operate until at least one section of resistor 92 has been inserted inseries with the field winding F of motor 5.

for combustion, float'39 will lower st farther causing the frame 53 to move downwardly. As the frame moves downwardly, contact will be made between contact members 79 and 80, and motor 96 will be caused to operate and drive drum 95 in the direction of arrow 101 with the result that motor 5 will be speeded up. The increased speed of motor 5 will be in accordance with the new position to which damper 8 has been moved.

f regulator frame 53 has been moved downwardly a predetermined amount, stop 88 will engage the lower L-shaped end of bar 82 whereby circuit controlling device 11 1S moved bodily downward to a position correspending to the position of the regulator so cuiticontrolling frame- The circuit controlling device 11 will, therefore, be in such small movements of re ator frame in either the upward or t e downward direction, the speed of motor 5 may be increased or decreased in accordance with relat1vely smallmovements of dam er 8 either'to its closed orlopen. position. 11 any event each time regulator frame 53 has moved down.- wardly a predetermined distance, bar 8? w ll be moved downwardly and carry with it ondevice 11 to a difierent position. By causing circuit controlling device 11 to move bodily with the regulator after 1t has moved a predetermined distance, the speedof motor 5 may be increased step-bystep as damper 8 is opened step-by-step. Regulator 17 operates to control the position of damper 15 and the speed of blower motor 13 in the same manner as re ulator 9 operates to control the position of amper 8 and the speed of blower motor 5. However, regulator 17, as stated hereinbefore, 1S afi'ected both by the pressure in duct 14 and the demand for steam upon header H of the boller. If the demand for steam on header H remains constant then variations 1n pressure in duct 14 Wlll cause variations in pressure within inverted bell 39 and the regulator will respond to either increase or decrease the speed of motor 13 in the same manner as regulator 9 operates to either increase or decrease the speed of motor 5.

. If. at any particular time the osltion of damper'l5 is such as to satisfy t e combustion conditions-within the furnace, but a demand for steam on header H is such that more combustion will be required in the furnace, then-valve 21 will be operated in the manner hereinbefore described to decrease the pressure in bellows 19 causing inverted bell 39 to move upwardly. As the bell moves upwardly, the regulator frame 53 will be caused to move downwardy to 0 en dampis en 15 andto increase the speed 0 motor 13.

In any caseif the regulatorll' is caused to operate damper 15 to a different position, the

7 speed a position that for of motor 13 will be causedtochange in the same direction as the damper is shifted or moved. The speed of motor 13 will follow the change in position of damper 15 whether such change be caused by variations in pressure in duct 14 by changes in pressure in header H or both. Bell 38 will come to rest and be in equilibrium with bellows 19 when the pressure in duct 14 has increased the proper amount in response to the in-. crease in fan or blower speed.

From the aboveit will be apparent to those skilled in the art that a system for controlling the speed of a blower in accordance with the position of a damper regulating the flow of air produced by the blower is disclosed. This system as described operates to change the blower speed step-by-step as the position of the damper is changed step-by-step. The system is so arranged that the amount of air flowing past the damper will be such that an appreciable change in the flow of air may be a'fiected by only a small change in the damper position.

While various modifications and changes ma be made in the invention as disclosed ,wit out departing from the s irit and the scope thereof, it is to be understood that only such limitations shall be placed on the invention as are imposed by the prior art and the appended claims.

What I claim as new and desire to secure by Letters Patent is: I

1. In combination with a boiler furnace having forced and induced draft fan blowers, a damperassociated with each blower, a driving motor for each blower, a regulator responsive to furnace pressure for actuating the forced draft blower damper, means controlled by said regulator for controlling the speed of the forced draft blower motor draft damper, a regulator responsive to the demand for steam for actuating said induced draft damper, and means controlled by said steam demand regulator for regulating the speed of the induced draft fan motor in accordance with the position of the induced draft damper.

2. In combination, actuatin means, a pressureactuated device contro led by said actuating means, a plurality of circuit controlling members, means operable by said actuated device for bodily moving said circuit controlling members, and means for holding said controlling members in any position to which they. may be moved by said pressure actuated device.

3. In combination, actuating means, a pressure regulator controlled by said actuating means, saidregulator having a movable member actuated thereby, an electric circuit controlling device, means for bodily moving said circuit controlling device in response to movements of said movable member, and

cuit controlling device arranged to be operated by said regulator and to be bodily moved thereby when said movable member has. travelled a predetermined distance.

6. In combination, a regulator having a movable member actuated by pressure, a cir- 4 cuit controlling device arranged to be operated by said regulator and to be bodily moved thereby when said movable member has travelled a predetermined distance and means for holding said circuit controlling device in any position to which it may be moved.

7. In combination, a regulator having a movable element actuated by pressure, means for causing said element to move in incremental steps, electric circuit controlling device, and means opcratively connecting said movable element and device disposed to effect successive movements thereof in response to predetermined increments of movement of said element.

8. In combination, actuating means, an ele ment actuatahle by pressure controlled by said means, circuit controlling device arranged to be actuated by said element to one positicui when said element is m vin one direction and to another circ :59 cor'relling position when moving in opp direction, and means operatively cc to element and de e points in the travel of ich the device is actuated rol ing positions. on, a regulator having a *rrenged for movement in condition to be controlled, device arranged to be member in response to a movement thereof, and means J. o ying the operative relation of said der cc and movable member that the dc ic may be operated at diii'erent points in stroke or travel said movable member in response o predetermined movements of said member throughout the full range of travel or stroke thereof.

10. In combination, a regulator having a movable member arranged for movement in accordance with a condition to be controlled, a circuit controlling device arranged to be operated by said member in response to a predetermined length of movement thereof, and means for causing said device to be operated at different points in the stroke of said movable member in re onse to predetermined movements of sai member throughs' out the full ran e of travel or stroke thereof.

11. In combination, actuating means, a pressure regulator controlled by said actuating means, an electric circuit controlling device actuated by said regulator at a definite point in the stroke of the regulator, and means actuatable by the regulator for chan ing the point in the stroke thereof at whic said device is actuated.

12. In combination, actuating means, a regulator controlled by said actuating means, an electric circuit controlling device havin a lost motion connection with and adapte to be operated in response to a definite movement of'the regulator, and means operated by the regulator for changing the point in the stroke of the regulator at which said device is operated when the movement of the regulator exceeds the limits of the lost mo- .tion permitted by the connection.

13. In combination, a regulator, two circuit controlling devices separately actuatable by said regulator, said devices being so disposed that the regulator must travel a distance in one direction or another suflicient to have operative connection therewith before one or the other of said devices is actuated thereby, and means operated by the regulator for concurrently displacing the points in the stroke of said regulator at which operative connection. is made with said de vices when movement of the regulator has exceeded amount required to connect operate said devices.

is. combination, regulator, two circuit co smiling devices separately actuat-able by regulator, said devices being so septhst the regulator must travel a predistance in one direction or anare one or the other of said devices is actuated thereby, and means wholly dependent on movements of the regulator for concurrently displacing the points in the strolre c the regulator at which said devices are a r thereby.

in combination, regulator having an element {adapted to move in one direction or another be ween two extreme positions in response to and in accordance with changes in variable to be controlled, a circuit controlling device ads ted to be to one circuit control ing posi'ion, when said element has moved a predetermined distance in one direction and to another circuit controlling position when said element moved a predetermined distance in the opposite direction, and means adapted to change the points in the travel of said element at which said device is operated to one or the other of its controlling positions when said element has moved a distance greater than said predetermined distance in either directicn.

16. In combination, a regulator having an element adapted to operate between two extreme positions, a circuit controlling device adapted to be actuated by said regulator element when it has moved a fractional part of its total travel towards one or the other of a fractional part of its total travel in one direction, and to the other circuit controlling position when the regulator element has moved a fractional part of its travel in the opposite direction, and means for maintaining said fractional-part travel relationship between said regulator element and device independently of the position of said element.

18; In combination, a regulator having an element adapted to operate between two extreme positlons, circuit controlling devices adapted to be actuated by said regulator element at points separated a distance equal to a fractional part of the total travel thereof, and means controlled by movement of the regulator for maintaining said fractionalpart travel relationshiplbetween said devices and regulator throug out the full stroke thereof.

19. In combination with a boiler furnace having forced and induced draft fan blowers, a damper associated with each blower, a driving motor for each blower, a regulator responsive to furnace pressure for actuating the forced draft blower damper, means controlled by said regulator for controlling the speed of the forced draft blower motor in accordance with the position of the forcedv draft damper, and a regulator responsive to the demand for steam or actuating said induced draft damper.

20. In combination with a boiler furnace having forced and induced draft fan blowers, a damper a driving motor for each blower, a regulator responsive to furnace pressure for actuating the forced draft blower damper, a regulator responsive to the demand for steam for actuating said induced draft damper, and means controlled'by said steam demand regulator for regulating the speed of the induced draft fanv motor in accordance with the position of the induced draft dam er.

21. In combination wit a duct having a damper therein, a fan blower connected to the duct, an adjustable speed motor for driving the fan blower, and apparatus for controllin the speed of the motor, of a regulator or operating the damper, means for operating the motor speed control apparatus,

said means havinga lost motion connection with and adapted to be operated by said regulator in response to a definite movement thereof so as to increase the speed of the fan driving motor as the dam r is moved toward open position and to ecrease the speed thereof as t e damper is moved toward closed position, and means operated by the regulator for changing the oint in the stroke of the regulator at whic operative connection is made with the means for operating said speed control ap ara-tus when the movement of the regulator lies exceeded the amount required to connect and operate the means having the lost motion connection therewith.

In testimony whereof, I have hereunto subscribed my name this 18th day of June, 1931.

. THOMAS A. PEEBLES.

associated with each blower, 

